The invention relates generally to safety apparatus for machinery requiring an operator, and specifically resides in a perimeter safety switch for such machinery which is easily accessible for quickly stopping machine operation.
Many stationary, upright machines require the presence of an operator for continuously operating the machine and supervising its operation. Many such machines require the use of both the operator's hands, which makes emergency stopping of the machine difficult and slow where conventional power switches are used. If the operator is momentarily disabled during an emergency condition, it may be virtually impossible to himself switch off the machine.
Stationary abrasive belt machines are a typical example. Such machines often employ an endless abrasive belt of substantial width passing over two or more cylindrical drums that operate at high linear speed and under significant power. They are typically used for production sanding, cross-abrading, deburring, polishing, surfacing and close tolerance machining. The endless abrasive belt operates horizontally or vertically at approximately the waist level of the operator, and is capable of continuous in-feed. Accordingly, the operator must manually feed or supervise automatic feeding of workpieces, and a second operator often receives the finished workpieces as they leave the machine.
Emergency or stop conditions for such a machine may arise for any number of reasons, among them equipment failure (motor burn-out, bearing seizure, belt breakage), the need for equipment readjustment, jamming of a workpiece within the machine, or accidental injury to an operator. Whatever the reason for the condition, it is almost always necessary to stop the machine immediately to prevent further injury to the operator, or to the equipment and workpieces. It is often difficult to stop the machine quickly, particularly where there are a plurality of operator's stations, if the machine is large, if the control switches are remote from the operator's area, or if the control switches are conventionally small in size. The problem may be compounded where human injury occurs and is accompanied by panic.
The subject invention remedies these problems with a perimeter safety switch that is accessible from any point of operation of the machine, and which can be actuated other than with the operator's hands. More specifically, the perimeter safety switch comprises a continuous longitudinal switch capable of being actuated at any point over its length, which is mounted on a bracket extending around the periphery of the machine, or at least around all areas which are accessible to the operator. The mounting bracket is disposed at approximately the waist level of the operator, and is spaced outwardly from the machine so that it is laterally beyond any other frame member or component of the machine.
Mounted in such fashion, the switch is easily accessible to the operator's hands, arms, lower torso, hips or upper legs notwithstanding the operator's normal position relative to the machine; and minimal contact with the switch by any such portion of the operator's body causes it to be immediately actuated. For example, if the operator is holding a workpiece relative to the abrasive belt with both hands when an emergency condition occurs, the machine is stopped simply by bumping it with the hip. If the operator is injured, either the operator himself or a co-worker can immediately stop the machine without searching for a switch which is remote or inaccessible, thus reducing the possibility of further injury and panic.
In addition to its improved operation, the inventive combination is structurally simple, easy to adapt to existing machines and inexpensive to install.